The invention relate in general to the field of electronic devices. More specifically the invention relates to a method and apparatus for restricting process fluid flow within a showerhead assembly.
Semiconductor fabrication typically includes depositing material onto a semiconductor substrate wafer and etching material from the substrate. Often these processes take place within a process chamber containing one or more wafers and a deposition apparatus referred to as a showerhead. The showerhead acts to direct process fluid to the semiconductor substrate wafer. The showerhead typically includes an inlet conduit connected to a process fluid source outside of the process chamber. And a showerhead plate with a number of holes extending therethrough to direct process fluid exiting the showerhead to the semiconductor substrate wafer. Showerheads are also used in both material deposition and etching processes to direct deposition and etching fluid to the semiconductor substrate wafer.
Problematic edge effects often result from uneven deposition and etch across the radius of a semiconductor substrate wafer. These problems often result when the characteristics of a plasma field or the flow of process fluid varies between the center of the wafer and the edge of the wafer. Such nonuniform deposition and etch often results in a semiconductor substrate wafer with disparate electrical properties across its radius. Because of this disparity portions of the wafer are often not usable for their intended purpose. In the case of circular wafers, inadequate deposition and etching of material adjacent to the outer edge of the wafer often renders devices formed adjacent to the outer edge of the wafer defective. As wafer diameter increases from six inches to eight inches to twelve inches and beyond, the number of devices formed adjacent to the outer edge increases significantly. Therefore, edge defects for a twelve inch wafer result in a greater number of unusable devices as compared with a six inch wafer.
One past solution for controlling deposition and etch across the radius of a wafer was to alter the geometry of holes extending through a showerhead plate. This technique allows process fluid to be directed toward selected areas of the substrate wafer. Simply, to increase process fluid flow to selected areas, more or larger holes are formed in the showerhead plate opposite those areas. However, this solution suffers from a number of drawbacks. First, a specialized showerhead plate is typically formed for a particular process and is often not useful for other processes Second, experimentation with a specialized showerhead plate is time consuming and expensive. A complete processing run is often required to evaluate the effectiveness of a particular geometry of holes in a showerhead plate. This consumes valuable resources and processing time. Third, the use of specialized showerhead plates for each deposition and etch process step can be costly, often requiring multiple showerhead assemblies to perform multiple processing steps and replacing showerhead assemblies to accomplish process changes.
In accordance with teachings of the present disclosure, a system and method are described for restricting process fluid flow within a showerhead assembly which substantially eliminates or reduces disadvantages and problems associated with prior apparatuses and methods used to deposit and etch materials during semiconductor fabrication. The apparatus includes a process chamber with a showerhead assembly disposed therein. The showerhead assembly includes a blocking assembly disposed within the showerhead assembly for restricting the flow of process fluid within the showerhead assembly. Restricting the flow of process fluid within the showerhead effectively restricts the flow of process fluid exiting the showerhead assembly, directed at a substrate wafer disposed within the process chamber.
In one aspect of the present invention a semiconductor processing apparatus is provided including a process chamber having a substrate support disposed within the process chamber operable to support a substrate wafer. A showerhead assembly is disposed within the process chamber facing the substrate support. The showerhead assembly has a showerhead plate that has passageways extending therethrough. An inlet conduit is coupled to the showerhead assembly to communicate process fluid from the exterior of the process chamber to the showerhead assembly. A blocking assembly is disposed within the showerhead assembly for restricting the flow of process fluid within the showerhead assembly.
In another aspect of the present invention a process fluid blocking assembly for controlling the flow of a process fluid through a showerhead apparatus used for semiconductor fabrication is disclosed. The process fluid blocking assembly includes a blocking device operable to be disposed adjacent to a showerhead plate such that the blocking device substantially restricts the flow of process fluid through a center portion of the showerhead plate.
More specifically, the blocking assembly may include a rod and a ring associated with the rod. The ring may be selectively moved between a first position along the rod and a second position along the rod. The blocking assembly also includes a plurality of linkages pivotally connecting the ring and an umbrella blocking assembly. A second end of each of the linkages is such that placing the ring in the first position expands the umbrella blocking assembly and placing the ring in the second position collapses the umbrella blocking assembly. When the umbrella blocking assembly is expanded, the umbrella blocking assembly acts to selectively restrict the flow of process fluid-through the showerhead assembly. When the umbrella blocking assembly is collapsed, the umbrella assembly allows substantially unrestricted process fluid flow through the showerhead.
In yet another aspect of the present invention a method for fabricating a semiconductor device on a substrate wafer disposed includes supplying process fluid to a showerhead assembly positioned opposite the substrate wafer. The method also includes selectively positioning a blocking assembly within the showerhead assembly to selectively restrict the flow of process fluid from the showerhead assembly to the substrate wafer. This selective positioning selectively effects the fabrication of the semiconductor device.
The present invention provides a number of technical advantages. One technical advantage is having a blocking assembly disposed within the showerhead assembly. The blocking assembly can selectively control deposition and etching on the outer edge of a semiconductor substrate wafer. This also allows the apparatus to selectively vary deposition and etch edge effects in a plurality of processes.
Another technical advantage is disposing an umbrella blocking assembly that can be expanded or collapsed within the showerhead assembly. This allows the apparatus to selectively control the deposition and etching of material across the radius of a semiconductor substrate wafer.